The interface between a heat sink and the component to which it is attached includes small voids due to surface irregularities, roughness, and lack of flatness of the two surfaces. These voids reduce the thermal transmissivity to the heat sink, and thus ultimately reduce the ability of the heat sink to dissipate heat generated by the component. In the past, it has been found that applying a film of thermal grease can diminish or substantially eliminate this problem. Thermal grease is well known in the art and can be a composition of silicone and zinc oxide, available from Dow Corning of Midland, Mich. and other sources. Another thermal grease composition, THERMALCOTE.TM. is available from Thermalloy, Inc. of Dallas, Tex.; another a product sold by the same company and known as THERMALCOTE II.TM. does not contain silicone. The THERMALCOTE.TM. products are available in forms that are applied by brush, squeezed out of a tube, applied by a paddle, or other techniques. Unfortunately, the application of thermal grease to individual components in a production environment is laborious, and inexact. Nonetheless, despite numerous efforts to create another interface material to replace it, thermal grease remains the most effective product for ensuring good thermal conductivity.
Thermal grease can be applied directly to an insulator strip. The coated strip is supplied in a package that must be peeled away, and the insulator must then be applied to a component. This product is sold under the name INSUL-COTE by Thermalloy, Inc. of Dallas, Tex. Similarly, it is known to apply a thin layer of thermal grease to both sides of an aluminum carrier that is 0.1 mm (0.004") thick. The coated carrier is then disposed between a heat sink and a microprocessor. This product is sold under the name CONDUCTA-COTE(TM) by Thermalloy, Inc. of Dallas, Tex. However, the use of such coated insulators or aluminum carriers does not eliminate the above-mentioned problems, since handling the grease-coated insulation or carrier is nearly as difficult as applying the grease from a tube or with a brush. The insulators and carriers can be obtained in strip form and applied by a machine, which alleviates some of these problems. However, this adds a production step and the capital cost of the application machine if the supplier of the pre-coated insulators or carriers does not provide one. The advantage of pre-coated insulators or carriers is that they apply a specific amount of grease, and a specific quantity of grease may be purchased by ordering coated insulators or carriers on a one-to-one basis with the heat sinks. However, a disadvantage of the above-described pre-coated insulators and aluminum carriers that are pre-coated with thermal grease is that they are difficult to manufacture.
As mentioned above, others in the art have attempted to create pads of material that serve as a replacement for thermal grease. Some of these products are insulating, while some more recent versions are not. Although such pads reduce the waste and inaccurate application related to the use of a thermal enhancement product, they are often more expensive and do not offer the thermal performance of grease. Therefore, it would be desirable to provide a product in which the thermal properties of grease are advantageously available to create a better thermal connection between a heat sink and a heat-emitting component. Moreover, it would be further desirable to reduce or eliminate waste, spillage and over-application of thermal grease. It is therefore an object of the present invention to provide products and methods in which thermal grease is applied in a precise and controlled manner. It is a further object of the present invention to provide products and methods that readily adapt to production environments and that do not require significant alteration of existing production sequences or changes in production tooling.
It is yet a further object of the present invention to provide a system and method for applying a substantially precise amount of thermal grease in a predetermined pattern.